About Kylin-PBC
Kylin-PBC is a periodic Density Functional Theory (DFT) program written in C++17, designed for high-accuracy electronic structure calculations of crystalline and periodic systems.
The program employs Gaussian-type orbital (GTO) basis sets with Goedecker-Teter-Hutter (GTH) pseudopotentials, and evaluates Coulomb and exchange integrals via advanced density fitting schemes: Multigrid Density Fitting (MGDF), Local Interpolative Separable Density Fitting (LSDF) and FFT-based Density Fitting (FTDF).
- Exchange-correlation functionals: LDA, GGA, meta-GGA, Hybrid and RSH
- Gamma-point (GRKS) and Monkhorst-Pack k-point sampling (KRKS) solvers
- Adaptively Compressed Exchange (ACE) acceleration for hybrid functionals
- Geometry optimization: BFGS quasi-Newton with trust radius control BFGS, RFO and GDIIS
- Transition State Search: NEB and ci-NEB with FIRE Optimizer.
- Occupation smearing schemes Fermi-Dirac, Gaussian and Methfessel-Paxton
Technical Capabilities
Core algorithmic components powering Kylin-PBC
Exchange-Correlation Functionals
Full hierarchy of Kohn-Sham DFT approximations through Libxc integration. Supports local density approximation through range-separated hybrids, enabling systematic accuracy benchmarking across Jacob's ladder.
Brillouin Zone Sampling
Monkhorst-Pack k-point meshes with automatic dispatch between Gamma-point (real-valued GRKS) and general k-point (complex-valued KRKS) solvers for optimal memory and computational efficiency.
Integral Algorithms
Three complementary density fitting schemes: Multigrid Density Fitting (MGDF) for Coulomb and pseudopotential matrix evaluation, Local Interpolative Separable Density Fitting (LSDF) for exchange matrix construction, and FFT-based Density Fitting (FTDF) for efficient exact exchange computation.
ACE Acceleration
Adaptively Compressed Exchange (ACE) operator with optional Cholesky decomposition dramatically reduces the cost of hybrid functional SCF iterations while preserving numerical accuracy.
Geometry Optimization
Analytical nuclear gradient-driven structural relaxation with BFGS quasi-Newton Hessian updates, trust-radius step control, and GDIIS/GEDIIS geometry extrapolation for accelerated convergence.
Transition State Search
Nudged Elastic Band (NEB) and Climbing Image NEB (CI-NEB) methods for locating minimum energy paths and transition states between reactant and product configurations on the potential energy surface.
Quick Start
Kylin-PBC requires two input files in the working directory: cell.txt (unit cell and atomic positions) and calc.txt (calculation parameters). Below is a minimal example for a silicon diamond single-point calculation.
# Silicon diamond — lattice vectors (Angstrom) 3.8396000862 0.0000000000 0.0000000000 1.9198000431 3.3251912150 0.0000000000 1.9198000431 1.1083970717 3.1350203425 Cart Si 0.000000000 0.000000000 0.000000000 Si 1.919800043 1.108397072 0.783755086
SCF.xcfun = PBE SCF.basis = dzvp-sr SCF.psudo = gth-pbe SCF.kmesh = 3 3 3 SCF.max_cycle = 100 SCF.eps_engy = 1e-8 [eV] SCF.hks_mix_method = BROY SCF.smear_method = fermi SCF.smear_sigma = 300 [K]